Centrifugal separating system



Aug. 26, 1969 B. A. FIERSTINE 3,463,316

CENTRIFUGAL SEPARATING SYSTEM Aug. 26, 1969 Filed June 19, 1968 e. A. FIERs-rlNE CENTRIFUGAL SEPARAT'ING SYSTEM s sheets-sheet 2 x oliofENms AT PusHgRjjLATE lSENSING FULLY I :DEVICE I }SENSES OPEN OLIDS INr i 1 RAW SLURRY FFLUEN l ENTERS SYSTEM a AND CLEAR I muoRl g l IS REMOVED I I I l I TIME CYCLE F IG. 4.

INVENTOR. BURTON A. FIERSTINE Aug. 26, 1969 B. A. FIERSTINE CENTRIFUGAL SEPARATING SYSTEM 5 Sheets-Sheet 3 Filed June 19, 1968 mm El l* *IITTI 3,463,316 CENTRIFUGAL SEPARATING SYSTEM Burton A. Ficrstine, Saginaw, Mich., assignor to Baker Perkins Inc., Saginaw, Mich., a corporation of New York Filed June 19, 1968, Ser. No. 738,175 Int. Cl. B04b 3/00; B01d 33/02 U.S. Cl. 210-78 19 Claims ABSTRACT OF THE DISCLOSURE A centrifugal separating system for separating solid `materials from liquid slurries or mixtures containing the same wherein the slurry or mixture is rotated in a circumferentially enclosed space for a time interval while liquid is axially drawn olf and then is released to a rotating perforated surface for another time interval during which the remainder of the liquid is drawn olf. The efficiency of the separating function in the first instance is controlled by a transducer which monitors the density of the effluent liquid of the system.

BACKGROUND OF THE INVENTION Field of the invention A liquid-solid separating system employing a centrifugal separator having an axially movable means for c011- .trolling the preremoval or separation function automatically.

Description of the prior art Continuously operating push-type, single stage centrifuge systems have long been employed for effecting the separation of liquid and solids. Since many of the mixtures and slurries to be separated are quite Viscous, many of the known push-type single stage centrifuge systems employed long baskets or screens to retain the caked solids collected thereon for a sufficient amount of time to achieve the desired degree of dryness. Another factor influencing the length of the basket or screens deals with a preliminary separating step which may be performed initially as the slurry enters the system. During this initial period, a preremoval of the greater proportion of the mother liquor may be effected prior to the admission of the material into the main centrifugal basket or screen. Manifestly, if the preremoval function is reasonably eficient, a shorter basket or screen can be utilized in the .main centrifuge station. Thus, by restricting the size of the basket or screen, less force will be required to discharge the solid caked material therefrom.

Summary One of the primary objects of the invention is to produce a centrifugal liquid-solid separating system which incorporates means for preremoval of a maximum portion of the liquid from a liquid-solid mixture prior to the time the mixture is allowed to pass to the main centrifugal separating basket and senses solid content in the effluent to automatically admit the pretreated mixture to the main separating basket to allow the solids to immediately form a firm cake thereon which can be readily removed.

Other objects of the invention may be achieved by a centrifugal separating system having a separating drum and an end wall therefor, drive means for moving one of said end wall and drum axially relative Ito one another; means for rotatably supporting said drum; and an imperforate distributor shell disposed in concentric relation with said drum and mounted for rotation therewith, said shell having a tapering interior surface with its end of largest diameter spaced from said end wall to 3,463,316 Patented Aug. 26, 1969 "ice form a feed passage therebetween; means revolving said drum and end wall; means for feeding a liquid and solid mixture to the opposite end of said distributor; signal generating means connected to said drive means for monitoring a solids content in the elluent flowing through said feed passage whereby when a predetermined quantity of solids is sensed by said signal generating means, a signal is generated to effect energization of said drive lto move said end wall relative to said drum.

Brief description of the drawings The above, as well as other, objects and advantages of the invention will be readily apparent to those skilled in the art from considering the following detailed description of an embodiment of the invention in the light of the accompanying drawings, in which:

FIGURE l is a fragmentary elevational view, partly in section, illustrating a centrifugal separating apparatus embodying the features of the invention;

FIGURE 2 is a sectional view of the apparatus illustrated in FIGURE 1 taken along line 2 2 thereof;

FIGURE 3 is a schematic illustration of the circuitry involved for effecting the energization of the drive means for controlling the preremoval of liquor from the liquidsolid mixture being treated; and

FIGURE 4 is a diagram illustrating a portion of the duty cycle of the apparatus illustrated in FIGURES 1, 2 and 3.

Description of the preferred embodiment Referring to FIGURES 1 to 3 of the drawings, there is illustrated a centrifugal separating system including a centrifugal separating machine having a main liquid housing 10. The main housing 10 is provided with a substantially cylindrical side wall 12, a back plate or end wall 14, and an access plate or panel 16. The housing I10 is further provided with a charging pipe 18 for the introduction of the liquidsolid slurry to be treated. The charging pipe 18 is disposed centrally of an opening in the apex end of a frustoconically shaped accelerating funnel member 20. A ilow distributing device 24 is mounted at the outlet end of the charging pipe 18 adjacent the apex of the funnel member 20. A cylindrical extension 22 of the apex end of the funnel member 20 is mounted within an inner race 26 of a bearing structure, while an associated outer race 28 is mounted within the innermost end of a horizontally disposed support tube 30. Ball bearings 29 are disposed between the inner race 26 and the outer race 28 to enable the accelerating funnel member 20 to be rotated relative to the support tube 30. It will be seen from an examination of FIGURE 1 that the support tube 30 is provided with an aperture 32 through which extends the charging pipe 18.

Immediately adjacent the larger open end of the funnel member 20 is a pusher plate 34 secured to one end of a shaft 36 which extends into and through-an exterior shaft 38. The pusher plate 34 is provided with an annular 'array of radially inwardly disposed fluid passages 40 extending therethrough. Pusher plate 34 and the accelerating funnel member 20 are interconnected in such fashion that they rotate in unison by :any suitable means such as pins 34a of square cross section fixed on the pusher plates 34 which are slidably received in openings 20a of like cross section in the funnel 20 so that the pusher plate 34 may be moved axially relative to the funnel member 20. At its front end funnel 20 is prevented from moving axially by the flange 20b.

Within the housing 10, coaxially of the cylindrical side wall 12, is a drum or basket B which includes a perforated cage 42 having a cylindrical formed interior screen 44 supported therein. The basket B further includes a hu'b 46 which is keyed or otherwise suitably affixed to the 3 end of the shaft 38. The coaxially arranged shafts 36 @and 38 are drivingly connected to a prime mover, not shown, which is capable of imparting rotary movement thereto. The shaft 36 is also movable axially with respect to the shaft 38 and is operated by circuits illustrated in FIGURE 3 to be explained in greater detail hereinafter.

The pusher plate 34 is provided with a pusher ring 48 suitably aflxed to the peripheral marginal edges thereof. The marginal edge of the pusher ring 48 is in close proximity to the innermost surface of the screen 44. It will be noted that the face of the pusher plate 34 facing the hub 46 is spaced sufficiently from the facing surface of the hub 46 to provide a fluid passage therebetween which communicates with the interior of the funnel member through the fluid passages 40.

The main housing 10 is partitioned by an iapertured partitional wall 50 into a wet housing 52 and a dry housing 54. The wet housing 52 is typically drained off through a discharge pipe 56. While the wet housing 52 is illustrated as .a single unobstructed chamber with a single outlet, it will be understood that in certain applications of the apparatus of the invention, the wet housing 52 m-ay be divided into a plurality of individual chambers all in communication with the perforated cage 42 of the drum or basket B. In such an embodiment, each of the chambers is provided with a separate discharge pipe.

Communicating with the open end of the drum or basket B and disposed within the dry housing 54 is a discharge ring 58 having an opening 60 at the bottom thereof. Further, the dry housing 54 is provided with a solids material discharge opening 62.

The structure thus far described may typically contain a sight glass assembly 64 disposed in the access plate 16 for visual inspection of a portion of the interior of the main housing 10 particularly in the region of the dry housing 54.

The basket hub 46 is bored as at 66 in radial alignment with a sighting aperture 68 formed in the end wall 14 of the main housing 10. A transducer device 70 is mounted exteriorly of the main housing 10 in alignment with the aperture 68 and the bore hole 66.

The shafts 36 and 38 are drivingly interconnected through a pusher control assembly C (illustrated in FIGURE 3) to the output shaft 80 of a prime mover capable of driving the shafts at any desired speed. Spaced apart bearing assemblies 82 and 84 are employed to rotatingly support the shafts 36, 38 and the control assemblyy C. Formed as an integral portion of the shaft 38 is a fluid actuated cylinder 86, the two portions of which are suitably secured together by threaded fasteners 88. A piston 90, keyed to the cylinder 86 so as to rotate therewith, is disposed within the cylinder 86 and is caused to reciprocate therein as will be explained hereinafter. The pusher control 'assembly C is of conventional design and is provided to control the forward movement of the piston 90 and the associated shaft 36 by admission or introduction of pressure fluid from a reservoir 92 provided with a suitable pump, through lines 94, 96, solenoid actuated valve 98, and the port 100. Upon such actuation, pressure fluid is admitted to the interior of the cylinder 86 to act against the outer face of the piston 90, causing the shaft 36 to force the pusher plate toward the accelerating funnel member 20. Simultaneously, fluid on the opposite face of the piston 90 is allowed to return to the reservoir 92 through the port 102, lines 104, 106, and the solenoid actuated valve 98. The opposite movement of the piston 90 and associated shaft 36 is conrolled by the introduction of pressure fluid from the reservoir 92 through the lines 106, 104, the solenoid actuated valve 98, and the port 102. Simultaneously, pressure fluid is allowed to return to the reservoir 92 from the other face of the piston 90 through the port 100, lines 96, 106, and the solenoid actuated valve 98. The reciprocal movement of the piston land the associated shaft 36 is typically limited by appropriate stops, not shown.

The solenoid actuated valve unit 98 includes solenoids 98a and 98b which are operative to actuate suitable valves upon an energization thereof through closing of switches x and y. The normally open switch x is closed by the return of pusher 34V to outward position and closes a time delay switch or timer T. The normally open switch y is closed by :a relay z energized by the transducer device 70 which is electrically coupled thereto through a signal generator and detector circuit 112 and an amplifier circuit 114. The switch x and a switch a may be provided in the path of an `actuator bar b, as shown in FIGURE 3. The transducer 70 may be of an ultrasonic type such as is illustrated and described in United States Patent No. 2,966,057 entitled Apparatus for Measuring Attenuation of Ultrasonic Energy, Robert B. Heller. More specifically, the transducer 70 includes fan electromagnetic stage for converting electric energy into mechanical energy which is transmitted through the aperture 68 of the lback plate 14 of the housing 10 and the bore hole 66 of the hub 46, and thence through the effluent liquor traveling through the fluid passage between the pusher plate 34 and the hub 46. A second stage of the transducer 70 receives the mechanical vibrations transmitted through the material being treated which is reflected back from the pusher plate 34.

The efuent liquor and solids (when they appear) These vibrations are then converted into electrical oscillations, the frequency of which is measured and is an indication of the attenuation or reflection suffered by the transmitted ultrasonic energy. The frequency of the chopped signal output is a function of the density of the transient fluid iowing through the fluid passage between the pusher plate 34 and the hub 46. Accordingly, the frequency of the reflected or retransmitted energy becomes a function of the solids content in the transient fluid being sensed by the transducer 70.

In operation, as indicated generally in the diagram illustrated in FIGURE 4, the raw slurry to be treated continuously enters the rotating accelerating funnel member 20 at its small end where the peripheral speed is relatively low through the feed or charging pipe 18. As the slurry passes down the inner face of the rotating funnel member 20, it is gradually accelerated until it reaches the large end thereof. At the start up of the operating cycle, the piston 90 of the cylinder 86 has forced the pusher plate 34 against the larger end of the funnel member 20 as shown in dotted lines in FIGURE l. At this time the rotating slurry initially comprises a radially outer annulus of liquid rich in solids and a radially inner annulus of liquid. 'Ihe output shaft 80 has caused the cooperatng shafts 36 and 38 to rotate, thereby simultaneously rotating the hub `46 and the associated basket B, the pusher plate 34, and the associated accelerating funnel member 20. During this preremoval or preconcentration period, a portion of the liquid content which has been centrifugally separated from the slurry is caused to flow through the fluid passage between the pusher plate 34 and the hub 46 and thence to the wet housing 52 through the screen 44 and the perforated cage 42 of the rotating drum or basket B. Finally, the liquid is carried from the system through the outlet pipe 56. As the solids content in the transient liquid increases because the outer annulus is entrapped, such increase is sensed by the scanner 70 and when the density thereof reaches a predetermined level the scanner 70 energizes the relay z to close switch y and energize solenoid 98b to actuate the valve 98 to allow pressure fluid to be admitted into the cylinder 86 through the lines 104 and inlet 102. At the same time, pressure uid discharges through lines 96 and 106 and the piston and associated shaft 36 are moved to the left as illustrated in FIGURE 3, causing the associated pusher plate 34 to move to the full line position illustrated in FIGURE 1. Through the centrifugal action, the slurry is now deposited on the internal screen surface 44 which lines the inner face of the basket B and the liquid content thereof is spun outwardly into the wet housing 52. This procedure is carried on for a predetermined timed cycle. When the plate 34 is moved outwardly switch x was closed and the timer T is started so that after a predetermined interval solenoid 98a is energized when time delay device T times out. Valve 98 is accordingly actuated to cause pressure iluid to be admitted to the cylinder 86 through the line 96 and inlet 100 once again while discharging through lines 102 and 94, forcing the pusher plate 34 again into position against the ring of the rotating accelerating funnel member 20'. As the pusher plate 34 and associated pusher ring 48 moves forward, it forces the solids material which have formed a cake on the internal screen 44 across the face of the rotating basket B. The filter cake (equal in thickness to the difference in the diameter of the outer edge of the funnel member 20 and the screen lining 44 of the basket B) is gradually pushed across the screen, and llies olf into the dry collector housing 54 through the outlet ring 58 and is nally exhausted from the system through the outlet 62. Obviously, simultaneously the mother liquor after passing through the screen 44 and the openings in the perforated cage -42 is collected in the wet housing 52 and discharged through the outlet 56. If washing is desired, a wash spray may be provided for even distribution of the wash liquid into the cake. While the transducer system is preferred, it may be possible with slurries having a very uniform character to substitute a time delay device T for the members 70, 112, and 114.

I claim:

1. A method of separating the components of a slurry having liquid and solid components comprising the steps of:

rotating the slurry in a circumferentially enclosed space to tend to form a radially outer rotating slurry annulus enriched in solids and a radially inner rotating slurry annulus more free of solids while blocking the discharge end of said space adjacent the outer annulus for a period of time;

removing liquid components axially from the inner annulus during said period of time;

opening the discharge end of said space adjacent said outer annulus during another interval of time to release concentrated slurry;

and receiving the concentrated slurry on a perforate revolving surface to radially express liquid remaining in the slurry therethrough by centrifugal force.

2. The method of claim 1 wherein slurry is continuously fed to a charge end of the space.

3. In a centrifugal separating system:

perforate drum means;

pusher wall means therein;

a frustoconical accelerator tube in said drum means having one end connected to said pusher wall means for rotary movement therewith;

means for rotating said perforate drum means and for rotating said pusher wall means;

and means for moving said pusher wall means toward said tube for a concentrating interval and thence moving it away from said tube for an interval during which concentrated slurry is released from the tube radially to the perforate drum means.

4. A method of separating the components of a slurry having liquid and solid components comprising the steps of:

rotating the slurry in a circumferentially enclosed space having a restricted discharge;

monitoring the discharge to determine when a predetermined concentration of one component has been reached therein;

and, when said concentration is reached, rotating the concentrated sl-urry in a perforate peripheral drum portion to separate the liquid components radially through the perforate portion while the heavy components remain therein.

S. In a centrifugal separating system for slurries having solid and liquid components:

a separating drum assembly including a radially outer perforate peripheral portion and a radially inner imperforate peripheral portion;

means for rotating said assembly;

generally radial wall means for substantially closing the imperforate portion but leaving passage means leading to said perforate portion;

means mounting said wall means and imperforate portion for relative axial movement;

means for sensing when the content of one of the components moving through said passage means reaches a predetermined concentration value; and

means operated responsively to said sensing means for moving said wall means and imperforate portion relatively axially apart when said value is reached.

6. The system of claim 5 wherein said imperforate portion comprises a tube inside said perforate portion and into one end of which said slurry is fed.

7. The system of claim 6 wherein said wall means cornprises a pusher wall received within said perforate portion to scrape the inner peripheral Wall thereof; and means is provided for moving said wall toward and away from the opposite end of said tube.

8. The system of claim 7 wherein said tube is frustoconical in shape and flares in a direction toward said pusher wall.

`9. The system of claim 7 wherein, when said wall is adjacent the tube, said perforate portion is behind the wall and passage means is provided through said wall to communicate with said perforate portion.

10. The system of claim 7 wherein means feeds slurry continuously to said one end of the tube; and said means for moving said wall is governed by timer means which holds said wall away from said opposite end of the tube for a predetermined time after which said wall is moved again toward said tube.

11. The system of claim 7 wherein said tube is connected to said wall for rotary movement therewith.

12. A method of preconcentrating a mixture of liquids and solids which includes the steps of introducing a mixture of liquid and solids to an enclosure having outlet means which is enlargeable;

subjecting the mixture to centrifugal action to remove a substantial portion of the liquid content from the mixture within the enclosure through the outlet means before it is enlarged; and

sensing the density of the effluent liquid and enlarging the outlet means of the enclosure upon an increase in density thereof above a predetermined level.

13. The method dened in claim 12 which includes the step of closing the outlet after a predetermined timed interval.

14. A centrifugal separating system having:

a separating drum;

a pusher plate assembly forming an end wall therefor;

drive means for moving one of said drum and said pusher plate axially relative to one another;

means for rotatably supporting said drum and said pusher plate;

an imperforate distributor shell disposed in concentric relation with said drum and mounted for rotation therewith, said shell having a tapering interior surface with its end of largest diameter disposed in facing relation with said pusher plate whereby when said pusher plate is moved axially away from the shell by said drive means a fluid material passageway is formed therebetween;

means for feeding a liquid and solid mixture into the interior of said distributor shell through the opposite end;

means for imparting rotating movement to said drum,

pusher plate, and distributor shell; and

signal generating means connected to said drive means for monitoring the solids content in the fluid material owing through said fluid material passageway whereby when said signal generating means senses a predetermined density of the iluid material a Signal is generated to effective energization of said drive means to move said pusher plate axially relative to said drum.

1S. The system defined in claim 14 wherein said pusher plate is provided with a plurality of passageways therein for the passage of the tluid material from the interior of the distributor shell to a sensing relation with said signal generating means.

16. The system defined in claim 14 wherein a timer eects reverse axial movement of said pusher plate to return the same to its initial position upon the expiration of a timed cycle.

17. Apparatus for separating the components of a slurry having liquid and solid components comprising:

concentrating housing means providing a circumferentially enclosed space having a discharge end; means for rotating the housing and thereby said slurry in said circumferentially enclosed space to tend to form a radially outer rotating slurry annulus enriched in solids and a radially inner rot-ating slurry annulus more free of solids; means for substantially blocking the discharge end of said space adjacent the radially outer portion of the housing means and outer annulus for a period of time;

means for receiving liquid components from the inner annulus during said period of time;

means for unblocking the discharge end of said space adjacent said radially outer portion of the housing and outer annulus during another interval of time to release concentrated slurry; and

a perforate revolving surface for receiving the concentrated slurry to radially express liquid remaining in the slurry therethrough by centrifugal force.

18. Apparatus for separating the components of a slurry having liquid and solid components comprising:

housing means having a chamber with a discharge opening;

means for rotating said housing means and the slurry in said chamber and centrifugally separating it into more and less liquid annulus portions;

means for receiving the more liquid portion out said discharge opening;

means for monitoring one of said portions to determine when a predetermined concentration of one component has been reached therein;

a perforate peripheral revolvable drum portion for receiving the less liquid portions to separate the liquid components radially through the perforate portion while the heavy components remain thereon;

means controlled by `said monitoring means for passing the less liquid portions to said drum portion when said concentration is reached;

and means for revolving said drum portion at a speed to centrifugally separate liquid components from the solid components.

19. Apparatus for preconcentrating a mixture of liquids and solids comprising:

References Cited UNITED STATES PATENTS 8/1959 Irving 210-376 2/1968 Ruegg 210-376 X JAMES L. DECESARE, Primary Examiner U.S. C1. X.R.

ZIO- 96, 376, 377 

